This is just the rears as I did the fronts the other day
This was done with Megs Wheel Brightener......started at 2:1 dilution as I thought that would be strong enough going by what Detailing World had to say however it just wasn't shifting some of the crap so a neat solution was done with a foam scouring pad and a bit of elbow grease and you see the results.
Some is still left on but that is now part of the alloy and would not shift in the slightest. I reckon that the dust has been building up over the last 7 years as I've never really had a good go at the alloys before and I doubt the previous owners had so no wonder that stuff is welded on....lol! I highly recommend Wheel Brightener anyway